Re: "Final" version of tty child frames

[Jared Finder <jared@finder.org>]

On 2025-01-04 22:46, Eli Zaretskii wrote:
>> Date: Sat, 04 Jan 2025 14:09:55 -0800
>> From: Jared Finder <jared@finder.org>
>> Cc: Eli Zaretskii <eliz@gnu.org>, gerd.moellmann@gmail.com,
>>  emacs-devel@gnu.org
>> 
>> TTY child frame cursors behave even worse under GPM and a TERM=linux
>> terminal.  In this case, the cursor ends up on some lines always
>> appearing at the end of lines (ignoring separate frames or windows) 
>> and
>> sometimes in the right place.  The point position is correct though 
>> and
>> the cursor does appear correctly once I start pressing simple keys 
>> like
>> 'A'.
>> 
>> Unfortunately, the redisplay code in Emacs is super hard for me to
>> understand and I can't figure out where or how the cursor gets
>> positioned.  If someone could give me some pointers here, I'd love to
>> investigate further.
> 
> If you mean the text cursor, then it is positioned by calling cmgoto,
> which is called from tty_cursor_to and tty_raw_cursor_to.
> 
> Frankly, I don't understand how the mouse could affect the cursor
> positioning.  Do you mean the cursor position is wrong when you click
> the mouse?

Emacs understanding of point ends up correct when I click the mouse, but 
the cursor is incorrect.  This only applies to some lines.  I get 
similar issues when using arrow keys for moving the point around as 
well.  I do not see the same behavior in an xterm.  This predates my 
change.  It only happens when tty child frames are visible with 
TERM=linux, as far as I can tell.

   -- MJF